"The Committee subpoenaed Trump Campaign Deputy Campaign Manager Rick Gates and former White House National Security Advisor Michael Flynn for documents and testimony. Both witnesses cooperated with the Special Counsel and provided substantial information about matters central to the Committee’s investigation", the release said.
Committee Chairman Adam Schiff said the refusal of both witnesses to cooperate with Congress is "simply unacceptable".
The release comes after the House passed on 11 June a resolution authorising congressional committees to take legal action against Attorney General William Barr, former White House Counsel Don McGahn and other Trump administration officials who may be defying subpoenas.
The administration is refusing to cooperate with House investigations, with President Donald Trump claiming Democratic lawmakers are attempting to overthrow a democratically elected president.
The back and forth between the administration and House Democrats comes amid growing calls to impeach Trump by rank and file Democratic lawmakers and demands for more evidence of presidential wrongdoing from House Speaker Nancy Pelosi before moving toward impeachment.
Russia has repeatedly denied US allegations that it interfered in the 2016 election, saying no evidence has been put forward to back up the accusations.
